1. Field of the Invention
The present invention relates to a washing system for a motor vehicle screen, and in particular but not exclusively to a valve assembly for use with such a washing system.
2. Description of the Related Art
Various washing systems which enable cleaning fluid to be delivered to clean headlamp screens and the like are known. In general they comprise a cleaning fluid source which is connected to a fluid delivery device which in an operational position can direct fluid onto the headlamp screen. Commonly the fluid delivery device will comprise a fixed nozzle, however for optimum performance it is often desirable for the nozzle to be close to the headlamp screen. With the present styling requirements of vehicles, it is increasingly found that this desired feature is difficult to achieve. Furthermore, for safety reasons, the nozzle should not be positioned so as to injure pedestrians in the case of an accident.
In order to overcome this problem, washing systems have been proposed in which the fluid delivery device is moveable between a retracted stand-by position and an extended operative position close to the headlamp screen. Such a known fluid delivery device is described in GB 2272363 which describes a telescopic washer which comprises a cylindrical housing having an inlet for the cleaning fluid. A nozzle carrier is mounted on a piston which is slidably mounted within the housing, and a nozzle is mounted on a distal end of the nozzle carrier which projects from the housing. The
Substitute specification filed Feb. 27, 2003 in application Ser. No. 10/019,677 nozzle carrier is normally held in retracted position within the housing by a return spring. When washing fluid is introduced into the housing through the inlet, the pressure of the fluid forces the piston against the return force of the return spring into an operative position in which the nozzle carrier projects from the housing. Thus, the nozzle is moved from an inoperative position, for example at the lower edge of a headlamp, to an operative position, for example perpendicularly opposite the center of the headlamp. Thus, the nozzle does not normally obstruct the headlamp, but is located in a position of maximum washing efficiency when in use.
The nozzle carrier is an elongate tube along which cleaning fluid can travel to the nozzle. When the supply of cleaning fluid is turned on, it is important that flow through the nozzle is not permitted until the washer is fully in its operative position. In order to provide this desired effect a valve is employed within the telescopic washer. The valve is selected.so that it opens to enable cleaning fluid to flow from the fluid reservoir to the nozzle only after the nozzle carrier is fully extended. Also the valve closes before the nozzle carrier begins to retract.
The telescopic washer system of GB 2272363 includes a housing within which a nozzle carrier is extendible under the action of cleaning fluid pressure entering the housing via an inlet port. The telescopic washer includes a valve to control delivery of cleaning fluid to the nozzle. However, a problem with the valve shown is that the valve is not constrained accurately once the valve has been opened. As a result, the valve requires locating portions to enable the valve to be located correctly on its return to the closed position. The valve is also susceptible to snagging as it slides within its recess.
Other valves have been suggested including so called proximity valves. These open and close not only under the influence of hydraulic pressures but are also structured to open once a portion of the washer system has been extended to a predetermined position. These types of valve require increased numbers of parts which therefore increases manufacturing costs and the possibility for product failure.
It is an object of the present invention to at least partly mitigate the above-referenced problems.
According to the present invention, there is provided a valve assembly for controlling the delivery of cleaning fluid to a washer system of a vehicle, comprising a valve seat having a fluid input port through which fluid can enter said valve assembly; a resilient valve member extending across the valve seat and having a central zone and at least one hole through said valve member formed peripherally of the central zone; valve biasing means for biasing said central zone against the valve seat to close the valve and thereby seal the fluid inlet port; and fixing means for fixing the peripheral edge of the valve member to the valve seat; wherein the central zone of said valve member may be displaced away from the valve seat under the action of fluid pressure in the inlet port to open the valve and allow the cleaning fluid to exit the valve assembly via said at least one hole.
Preferably the valve member comprises a valve assembly, wherein said valve member comprises a diaphragm constructed from a resilient material and having a generally flat central zone for sealing the fluid inlet port; and a plurality of holes disposed peripherally around said central zone, when said valve member is displaced, to allow fluid to flow from said inlet through said holes to an exit of the valve assembly.
According to the present invention, there is also provided a washer system including the valve assembly, in which said system comprises a telescopic fluid delivery system comprising a piston/cylinder combination connectable to a cleaning fluid source, one of the piston and cylinder being moveable relative to the other under the action of fluid pressure to extend an elongate nozzle support portion which supports a nozzle at its distal end for the delivery of cleaning fluid.